1. Field of the Invention
The present invention relates to footwear and is directed more particularly to an insert, a shoe including the insert, and methods for making same.
2. Description of the Prior Art
There have been numerous attempts to provide an insert for use in footwear that will maintain comfortable temperature of a foot by allowing air to circulate freely around the foot and directing moisture away from the foot. Moisture creates a problem in both cold and warm weather because of its high degree of temperature conductivity. Accordingly, dissipation of moisture underfoot is critical in stabilizing temperature of the foot.
There have also been attempts to provide a footwear insert with substantial cushioning, impact absorption and energy return capabilities. In addition to providing added comfort, these features prevent damage to the foot during exercise. It is desirable to provide an insert which will withstand the forces of impact over a long period of time.
In U.S. Pat. No. Re 24,007 there is disclosed a corrugated fabric that is resilient and is capable of returning repeatedly to its hollow shape after it is compressed. The fabric permits the free flow of air along its corrugated channels. It has good insulating properties to provide protection from heat or cold. It was originally thought that the material could be used as an insert for the sole of a shoe to provide cushioning, or as a liner for cold weather boots to provide thermal insulation. It was found, however, that pressures on the fabric in use caused flattening of the corrugated separating fabric, with the result that the air channels between the two woven fabrics were so compressed that insulation due to the air in the corrugated channels and cooling due to circulation of air through the channels, were substantially eliminated.
U.S Pat. No. 4,073,072 to Gross sought to eliminate problems of collapsible air channels by providing a structure comprising two mesh-like fabrics woven from a solid monofilament plastic material, which fabrics are separated by corrugated separating material. The two fabrics are joined to the separating material, such that the separating material forms a structure which resists deformation of the first and second mesh-like plastic fabrics toward each other upon application of a compressive force. Although the structure provides an air space, it does not provide for energy return. In addition, the structure will not compress to a degree that allows for pumping action to assist air in circulating around the foot.
As noted above, cushioning and energy return are beneficial attributes of a footwear insert. U.S. Pat. No. 4,656,760 to Tonkel, et al, shows a cellular insert formed of a series of cellular shaped components having voids filled with foam and forming part of the sole of a shoe. The insert serves as a means for reinforcing the foam which cushions, or absorbs, the forces of impact exerted upon the shoe during use. Disadvantages of this insert are that it lacks space for air to circulate and, thus, can cause the foot to become excessively hot or cold, and the insert allows moisture to build up on the foot.